Added a new statemachine AIFetchInventoryFolder, which can be used
to fetch the contents of a folder by name or UUID.
Also added AIEvent (and one event,
AIEvent::LLInventoryModel_mIsAgentInvUsable_true, which is needed
for AIFetchInventoryFolder).
Fixed LLInventoryModel::sBackgroundFetchActive to correctly reflect
whether or not LLInventoryModel::backgroundFetch is added to
gIdleCallbacks.
Avoid duplicated entries in sFetchQueue.
Reset sFullFetchStarted in LLInventoryModel::stopBackgroundFetch to
allow for a renewed full fetch when some single-folder fetch stops it.
Added AIStateMachine::mQueued to make calling 'cont()' more robust:
calling cont() / idle() / cont() on a row would otherwise add a
statemachine twice to the active list, which would cause a crash
when it's killed.
Call AIFilePicker::create() instead of new AIFilePicker.
Renamed deleteMe() to kill() and bs_deleted to bs_killed.
Only default to auto destruct when created with create(true),
otherwise kill() has to be called explicitely.
Also upgrade the file picker filters with the new extensions found
in the orginal file picker code of Singularity.
Also improve AIFilePicker a bit: added hasFilename() and now
deleting the statemachine automatically by default: it's no longer
needed to call deleteMe from the callback.
This is the skeleton needed to implement classes that can be reused and
work together, which can perform asynchronous tasks (read: need to wait
for certain events before they can continue).
An example would be the task of waiting for a given inventory folder to
be read. This could then be used to improve the builtin AO
(automatically reading that folder when a notecard is dropped, and
continuing when the whole folder is read).
It's first use will be communication with a filepicker that runs
in a plugin.
